Generally, it is a good idea to allow animals with heart disease to have free access to water. Many different diseases and medications may cause a dog or cat to urinate more (or less), so it is important for a pet to always have access to plenty of water. Diuretics such as furosemide (Lasix®) lead to increased urine output and increased thirst, and unless free access to water is permitted these animals might get dehydrated. Changes in normal patterns of drinking and urinating should be noted and discussed with the veterinarian. While there are certain situations where limiting water intake might be desirable, this should only be undertaken under close supervision of your veterinarian.